A global system for mobile communication (GSM) is a radio technology which has been developed as a system for standardizing radio communication systems in. A general packet radio service (GPRS) is a technique introduced to provide a packet switched data service in a circuit switched data service provided from the GSM. A universal mobile telecommunication system (UMTS) is a wireless communication system based on wideband code division multiple access (WCDMA). E-UTRAN is a wireless communication system based on orthogonal frequency division multiple access (OFDMA).
To overcome a restriction of a service area and a limitation of a user capacity, the wireless communication system provides a communication service by dividing the service area into a plurality of cells. This is referred to as a multi-cell environment.
Cell selection is a process in which a mobile station (MS) selects a cell to receive a service. The purpose of the cell selection is to register the MS to a network in order to receive the service from a base station (BS). In general, the MS selects a cell having a strongest signal property value by performing a signal measurement process with respect to the BS in all searchable frequency bands. The cell selected by the MS is referred to as a serving cell. A cell neighboring to the serving cell is referred to as a neighbor cell.
When the MS moves from one place to another, it may be inappropriate to receive the service from the serving cell. In this case, the MS reselects a suitable cell capable of maintaining service quality and receiving a signal with better quality. This is referred to as cell reselection. The cell reselection is a process of selecting a more suitable cell based on criteria for cell reselection and signal measurement in an idle state. In the idle state, the MS repeats a process of reselecting a cell having a better signal property by measuring signals in the serving cell and the neighbor cell. For the MS with mobility, the cell reselection is important in order to receive a service with better quality.
The MS may belong to one or more closed subscriber groups (CSGs). If the MS belongs to the CSG, at least one CSG identity (ID) may be included in a CSG whitelist of the MS. The CSG whitelist is provided by a non-access-stratum (NAS), and is a list including CSG IDs of all CSGs to which a subscriber belongs. If the MS belongs to at least one CSG, the MS additionally uses an autonomous search function for UTRAN and/or E-UTRAN CSG cells in general cell reselection. The section 6.6.7 of 3GPP TS 45.008 V9.1.0 (2009-11) “3rd generation Partnership Project; Technical Specification Group GSM/EDGE Radio Access Network; Radio subsystem link control (Release 9)” can be incorporated herein by reference for description of the cell reselection to the CSG cell. If the strongest cell detected by the MS from the UTRAN or E-UTRAN cells is a proper CSG cell, the MS reselects the CSG cell irrespective of a cell reselection rule for a cell currently accessed. If the MS does not have the CSG whitelist or if the CSG whitelist is empty, the MS does not use the autonomous search function for the CSG cell. The network provides the MS with information regarding a dedicated UTRAN CSG frequency and/or a dedicated E-UTRAN CSG frequency. If the MS does not have the CSG whitelist or if the CSG whitelist is empty, the MS ignores a corresponding frequency for measurement and cell reselection.
The network can request the MS to send a measurement report and can control cell reselection of the MS. This can be referred to as network controlled cell reselection. The section of 3GPP TS 45.008 V9.1.0 (2009-11) “3rd generation Partnership Project; Technical Specification Group GSM/EDGE Radio Access Network; Radio subsystem link control (Release 9)” can be incorporated herein by reference for the description of the network controlled cell reselection. The network controlled cell reselection can be performed depending on a mode such as NC0, NC1, NC2, etc. In the NC0 mode, the MS performs autonomous cell reselection. In the NC1 mode, the MS reports a measurement result to the network and performs autonomous cell reselection. In the NC2 mode, the MS reports the measurement result to the network, and performs the autonomous cell reselection only when cell reselection is triggered for a case of downlink signaling failure, random access failure, cell access prohibition, etc. The network controlled cell reselection can be performed by using a packet cell change order (PCCO) message. A set of measurement report parameters can be transmitted to the MS by using the PCCO message.
For mobility of the MS, the network controlled cell reselection can be supported with respect to CSG cells. Various methods can be proposed to support the network controlled cell reselection for the CSG cells. In particular, there is a need for an effective method for overcoming inefficiency and complexity of the conventional method.